Electric blasting device using aluminum foil

ABSTRACT

The present invention relates to an electric blasting device using aluminum foil, the objective of which lies in providing an economical and safe electric blasting device. In line with this objective; a portion of the outer conductor of the cable is removed, and the aluminum foil is inserted therein in order to electrically connect the inner and outer conductors. Between the aluminum foil and the inner conductor, water, an insulator, and a teflon tube are inserted. When pulse high-current is made to flow, the aluminum foil changes into the condition of plasma. The aluminum therefrom and water react to generate explosive power. The invention is economical in that it uses commercialized aluminum foil, in addition to having a short scattering distance of the fragments. It also allows a low-vibration blasting due to the short reaction time therein.

TECHNICAL FIELD

The present invention relates to an electric blasting device, or morespecifically to an electric blasting device using aluminum foil.

BACKGROUND ART

An electric blasting device has many advantages over the conventionalblasting device, e.g., explosives or dynamites, in that it generatesless vibration and noise with almost no spattering fragments. Theconventional electric blasting devices of the past utilize customizedaluminum wires or use a kneaded mixture of aluminum powder and water asexplosives in order to cause chemical reactions therein. However, thissort of methods are problematic for the following reasons: (a) they mustuse customized aluminum wires or powder, which are difficult to find inthe marketplace; (b) the reaction time is extended therein; and (c) theissue of safety arises due to the far-scattering fragments from blastinga bedrock.

SUMMARY OF THE INVENTION

In line with solving the aforementioned problems, the objective of thepresent invention lies in providing an economical and safe electricblasting device and an aluminum foil installation structure by means ofusing aluminum foil which is easily accessible in the marketplace,Instead of using hard-to-obtain aluminum powder or wires.

The present invention relates to an electric blasting device usingaluminum foil, the objective of which lies in providing an economicaland safe electric blasting device. In line with this objective, aportion of the outer conductor of the cable is removed, and the aluminumfoil is inserted therein in order to electrically connect the inner andouter conductors. Between the aluminum foil and the inner conductor,water, an insulator, and a teflon tube are inserted. When pulsehigh-current is made to flow, the aluminum foil changes into thecondition of plasmas and the aluminum therefrom and water react togenerate explosive power.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an outlined drawing of the electric blasting device usingaluminum foil under the present invention.

FIG. 2 is a cross-sectional drawing of the coaxial cable used in theelectric blasting device using aluminum foil under the presentinvention.

FIG. 3 is an outlined drawing of the cable terminal under the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The composition and the functions of the present invention, withreferences to attached drawings, are explained in detail as below. FIG.1 is an outline drawing of the electric blasting device using aluminumfoil under the present invention. As illustrated in FIG. 1, the electricblasting device of the present invention comprises a coaxial cable orthe similar structure thereof (1), a cable terminal (2) for connectingsaid coaxial cable to the aluminum foil, a foil holder (3) for holdingthe aluminum foil (4) in a fixed position to said cable terminal (2),and aluminum foil (4) for generating explosive power by causing chemicalreactions with water.

As shown in FIG. 2, the coaxial cable or the similar structure thereof(1) comprises, from the center to the outside, an inner conductor (8),an insulator (7), an outer conductor (9), and an outer covering (10).The outer conductor (9) of the coaxial cable (1) is removed to theextent necessary, and a teflon tube (6) is inserted to prevent damage tothe insulator (7). However, in some cases, a teflon tube (6) may not benecessary. The aluminum foil (4) which generates explosive power is madeto cover the terminal (2) which is attached to the inner and outerconductors of the coaxial cable (1). With the attachment of the aluminumfoil (4) to the cable terminal (2) in this manner, the outer conductor(9) of the coaxial cable (1) is electrically connected to the innerconductor (8) thereof. Between the teflon tube (6) and the aluminum foil(4), a small space is provided to be filled with water. Small holes aremade in the aluminum foil for filling the interior with water.

Having such structure as above, the electric blasting device of thepresent invention is made to operate with the following principles: Whena high-current pulse flows through the aluminum foil (4), heat isgenerated by resistance of the aluminum foil (4), causing a furtherincrease in resistance of the aluminum foil (4). Consequently, more heatis generated, increasing in a non-linear manner, and most of the energystored in the capacitor is consumed by the aluminum foil (4). Since mostof the energy is consumed in such an intensified manner, the aluminumfoil becomes evaporated, in effect, turning into plasma. Expansion forceis primarily generated by volume expansion of the aluminum, and thesecondary chemical energy is emitted by reaction of aluminum plasma withoxygen in water. Consequently, the pressure is further increased, andthe explosive power is so generated.

Here, the optimal cross-sectional area and the length of the aluminumfoil can be calculated from the following Mathematical Formulas 1 and 2.If the formulas are satisfied, the point of energy consumption byaluminum foil (4) is at the current. All of the energy consumed isminimized, thereby generating more power.

Mathematical Formula 1

$\begin{matrix}{A^{2} = \frac{E^{3/2}}{{VL}_{S}^{1/2}K_{v}}} & {{Mathematical}\quad {Formula}\quad 1}\end{matrix}$

Mathematical Formula 2

$\begin{matrix}{l = \frac{{EL}_{L}}{\rho_{m}A\quad {\zeta ( {L_{S} + L_{l}} )}}} & {{Mathematical}\quad {Formula}\quad 2}\end{matrix}$

Here, A is the cross-sectional area. l is length. E is the energy storedby a capacitor at voltage V. L_(s) is a circuit inductance. L_(L) is aload inductance. P_(m) is density. ζ is evaporation energy. K_(v) is aconstant. For the material constants with respect to aluminum, P_(m) is10.5×10³ kg/m³, K_(v) is 2.2×10¹⁶ [MKS], and ζ is 10.8×10⁶J/kg.

FIG. 2 is a cross-sectional drawing of the coaxial cable (1) used in theelectric blasting device utilizing aluminum foil of the presentinvention. There, the coaxial cable (1) comprises an inner conductor(8), an outer conductor (9), an insulator (7) inserted between the twoconductors, and a protective outer covering or stainless steel pipeprotective structure (10).

FIG. 3 is an outline drawing of the cable terminal (2) used in thepresent invention. The cable terminal (2) comprises a female screw (11),a contact ring (12), and a male screw (13). When screws (11) and (13)are screwed into place, the contact ring (12) is compressed andtightened firmly against the cable (1). As such, an electric contact ismade while enabling terminal (2) to withstand the mechanical forcetherein. The advantages of the present structure lie in achievingcoaxiality which reduces unnecessary inductance and in effectivelywithstanding the magnetic force generated by pulse high-current.

As compared to the conventional explosives and dynamites used in theconstruction sites, i.e., for blasting bedrock and buildings, anddismantling concrete structures, a blasting device utilizing a veryeconomical and safe aluminum foil by means of the present invention canbe used as a replacement therein.

Further, as compared to the conventional electric blasting devicesutilizing aluminum wires or powder, the present invention is highlyeconomical in that it uses an ordinary commercialized aluminum foil,allows low-vibration blasting due to the short reaction time, andenhances safety due to the short scattering distance at the time ofblasting.

Further, with easy installation, the present invention by using acoaxial cable structure can minimize the inductance of the transmissionline, and is highly effective due to its symmetrical structure.

What is claimed is:
 1. An electric blasting device, which comprises: (a)a coaxial cable comprising a coaxial inner conductor at the center, anouter conductor, and an insulator for insulating said outer and innerconductors; (b) aluminum foil; (c) a cable terminal which connects saidcoaxial cable and said aluminum foil: (d) a teflon tube which isinserted onto said inner conductor for preventing damage thereto; (e) aninsulator for insulating said inner and outer conductors; (f) water,inserted between said aluminum foil and the teflon tube, at a locationfor enabling the water to react with the aluminum foil; and (g) saidaluminum foil, after removing a certain portion of the outer conductorof said coaxial cable, to the extent necessary for blasting, which isinserted therein to electrically connect the outer conductor of saidcoaxial cable to the inner conductor, thereby attaching onto the cableterminal through a foil holder, said aluminum foil and the water beingarranged to provide a reaction for generating explosive power.
 2. Anelectric blasting device according to claim 1, wherein said cableterminal comprises a female screw, a male screw, and a contact ring, andsaid male screw is connected to the female screw through said contactring.
 3. An electric blasting device for connection to a coaxial cableand for activation to provide explosive power in response to ahigh-voltage pulse being applied between inner and outer conductors ofthe coaxial cable, the blasting device comprising a coaxial connectorfor connecting the inner and outer conductors of the cable to first andsecond coaxial conductors of the blasting device, the first and secondcoaxial conductors of the blasting device being respectively inner andouter conductors of the blasting device, the second conductor includinga metal that vaporizes and forms a plasma in response to thehigh-voltage pulse being applied by the coaxial connector to the firstand second coaxial conductors, a solid insulator between the first andsecond conductors, a volume for receiving a liquid between an exteriorsurface of the solid insulator and an interior surface of the metal; theconnector, the first and second conductors, the insulator and the volumebeing such that in response to the pulse being applied to the connectorby the conductors of the cable a discharge current for causing theexplosive power flows between the first and second conductors, throughthe insulator and the liquid when the liquid is in the volume.
 4. Thedevice of claim 3 wherein the metal is a tube shaped foil.
 5. The deviceof claim 4 wherein the foil includes openings for enabling the liquid tobe poured into the volume.
 6. The device of claim 5 further includingthe liquid in the volume.
 7. The device of claim 6 wherein the foil andthe liquid are respectively aluminum and water.
 8. The device of claim 3wherein a solid structure in the device includes openings for enablingthe liquid to be poured into the volume.
 9. The device of claim 3further including the liquid in the volume.
 10. The device of claim 9wherein the foil and the liquid respectively include aluminum and water.11. The device of claim 10 wherein the metal is aluminum foil.
 12. Thedevice of claim 11 wherein the aluminum foil is shaped as a tube. 13.The device of claim 12 further including a metal protective structurecoaxial with the first and second conductors and surrounding the secondconductor.